722.364 Transmission 1990 SL500 - PeachParts Mercedes-Benz Forum

fcicco · #1 12-02-2005, 11:59 AM

Transmission slips in reverse only when warm. First thing in the morning it only slips a little. As I drive, need very high RPM to engage in reverse but it always engages. Bought the car with 97K miles and transmission was fine - Problem started @ 110K - it has 120K now. Did the filter and fluid thing @ 110K and the problem remained the same. Does not seem and better or worse since.

jhodg5ck · #2 12-02-2005, 07:12 PM

you might up the modulator pressure a bit... Sounds like your trans is on the way out though.
Have you triple checked your fluid level?

Jonathan

rschleicher · #3 12-02-2005, 09:04 PM

Unfortunately, reverse is what usually goes out first on these transmissions. Although your miles total is pretty low. My reverse (722.3 transmission, in a 1991 420SEL) went out at 167,000 miles. For several months the early symptom was that it was taking longer and longer (up to seconds) for reverse to engage. Then it would do it when cold, but not engage at all when hot, unless I "blipped" the gas a bunch of times. Then it wouldn't even engage when cold.

To verify that a modulator adjustment won't help, you can try temporarily removing the vacuum line at the modulator end (and plugging the dangling line with a golf tee, or small pencil). With the vacuum line disconnected all of your shifts should be super crisp/firm/hard. But, you are likely to see no change in the engagement of reverse.

In older 722 transmissions (.0, .1, and .2), there was an externally-adjustable reverse band, which would have allowed a cheap fix. Unfortunately, the 722.3 and later 722 transmissions have a reverse clutch, instead of a band design. When this fails or wears out the only remedy is to remove and open up the transmission, and replace the B3 clutch. Depending on how long you plan on owning the car, and how the rest of the tranny looks inside, you can then decide on either just repairing the B3 clutch (and putting in new seals while at it), or going for a full-scale rebuild. In my case, at generally-high SF Bay Area prices, the cost estimate was $1300 for the B3 repair, versus $2,600 for a rebuild. The third option is to just get a replacement (remanufactured) transmission. But that route sort of precludes the opening up of the old transmission, without incurring some degree of "double expense". The prices I quoted above were at an independent transmission shop that had a local reputation for good expertise (including rebuilding, and not just replacing), and honesty. After removing and opening my tranny, the head mechanic told me that the rest of it (except reverse) looked pretty good, even at 167,000 miles, and therefore he saw no compelling reason to do more than the B3 repair. I now have 182,000 miles, with no further problems.

jhodg5ck · #4 12-02-2005, 11:03 PM

Well said, I mentioned the modulator as when I've had cars in w/ cars that were slow to engage in reverse they typically were not shifting 100% as they should in other gears, but the change was over enough time that most owners didn't realise/know the difference.

I have found on transmissions that are on their way out/experiencing excess clutch wear that upping the mod pressure can buy 10-15,000 miles allowing time to save for a proper rebuild.

Jonathan

blueranger · #5 12-02-2005, 11:07 PM

how do you up the mod preasure..

i have an 83 300sd

HerbPhillips · #6 12-03-2005, 07:30 PM

I replace the reverse frictions in 722.2,.3,.4,and .5 all the time.

I buy and sell old MB's for a living. We encounter reverse friction failure all of the time, mostly in heavy cars like the W140 and especially the w124 wagon.

It's an easy fix. Have the trans pulled. Go to a trans parts supplier like DACCO DETROIT and get the five friction discs (they are asbestos lined like a brake pad). Pull the torque converter out and remove the front pump. The reverse frictions and steels are behind the front pump.

Takes 15 minutes or so after trans is pulled. We ususually buy the re-seal kit and replace all the front pump o-rings when we do the job.

The frictions are like $2.50 each from a trans parts supplier (and $35/ea from MB), the reseal kit is about $90 or so for all the rubber in the trans.

C32AMG · #7 12-03-2005, 07:50 PM

B3 clutches are worn, it’s an internal problem.

fcicco · #8 12-05-2005, 11:38 AM

Car is 1995 SL500 not 1990.
I don't have a problem pulling the transmission myself - I've done it a few times with some help. It is a lot of work..so if I do pull it, I would have the transmission rebuilt. I live in Erie, Pa but no one here (that has a good reputation) will do the rebuild. If someone knows of a good shop within a 50 mile radius, I would consider taking the transmission to that shop.
I can get a rebuilt transmission from several sources for $ 1500 to $ 2100 with a new torque converter - 2yr warranty but these places have mixed reveiws on several forums. Any recommendations if I go that route ??
Thanks .. Fred

HerbPhillips · #9 12-05-2005, 12:19 PM

I'm not a guru and I can't answer in a manner that is very detailed, but...

If he pulls the trans, removes the torque converter (slides out) , and unbolts the front pump, sets it on his bench, then carefully removes the forward gears, he will be right @ B3. It takes about 20 minutes to reach this. He probably only needs the frictions, and they are only like $2.50 each. There should be 4 I think. He then can bolt it back together and it will have reverse, unless some other problem other than wear caused the frictions to wear out. I fixed a 722.507 last month like this in a 1996 SL320 w/slipping reverse.

fcicco · #10 12-22-2005, 11:38 AM

I have decided to replace the transmission..diy. I have serveral manuals as well as All Data instructions. Does anyone have any tips, tricks or traps that I should be aware of ???
Found a rebuilt transmission (722.364) from Sun Valley in CA. $1295 w/Torque converter, two year warranty. Does anyone have any feedback.. pro or con about this company ???
Thanks and seasons best to all.
Fred